Thanks everyone for the good conversation, I am sure that many looking in are really enjoying the friendly exchanges of technical hewing information
Personally I always hewed from the butt to the top on the rough pass, quickly knocking away about 75% of the wood from the face of the cut, Then I apply finish scoring every 4" to the rough hewn face, and work backwards as I finish the surface with my single beveled broad axe-- to the line or splitting it!
One thing that is important is to apply the scoring at an acute angle away from the direction you are hewing, so that the chips fall away and don't hang up--this seems to be a minor detail but will aid dramatically your efforts to leave a good surface
As I finish the first side, I roll the flat surface up (and level it), secure it, and line the second side on the flat surface from end to end.
Now as you hew the second side you will have a good flat surface to stand on and score between your feet as you ready yourself for the hewing process to begin
Another thing I always did was as I finished each side I would stand directly at the end and visually cast my eye from end to end and see if by chance I needed to correct the vertical face near the centre of the new hewn side, at that point I would go back and touch up if necessary
As a closing remark, I would like to say that in all my years of hewing I never sat down to hew, but if it works for you be my guest
Another thing that I might add is that I do believe that you are placing too much emphasis on the exterior face, just do a good job and be satisfied
Many of the log homes I have examined show clearly the axe marks in the finished surface, and I might add pretty well all the logs used for this purpose are red cedar